Sometime you may need to access a database by a certain title or vendor. For instance, the database publishers, the people who compile the information that is covered within the topic area of a particular database, will put together several such databases on a variety of topics. Each database will have it's own unique information but will be linked by the interface (they way you search) depending on the vendor. You may favor one vendor over another because they have better results, look better or are easier to use.
Some vendors will have several databases such as EBSCO which supplies over 50 databases alone and Gale which supplies 5 searchable databases or some which will just offer the one such as CQ Researcher, Credo and JSTOR to name a few. The benefit of searching by vendor is that if you know an article you are looking for is in an EBSCO database, or you simply like EBSCO's selection over the other, you can perform a search across ALL EBSCO databases instead of each one individually!
Simply check the box marked "Select/deselect all"
And you can search all 50+ databases at once.
You may also select individual databases by their titles. This can come in handy when you know exactly which database you want to access. For instance, if you instructor points you to a specific article that you can find in a specific database, you can easily navigate there using the Alphabetical by Title list rather than trying to determine which subject area that database in question falls under. Or say you found an article initially in GeoRef that you would like to access again